Coating compositions

ABSTRACT

THIS INVENTION RELATES TO FIBROUS SUBSTRATES AND THE SEQUENTIAL COATING THEREOF WITH AN INTERPOLYMER OF ETHYLENE, VINYL CHLORIDE AND ACRYLAMIDE AND POLYVINYLIDENE CHLORIDE POLYMER.

United States Patent 3,567,491 COATING COMPOSITIONS Paul R. Graham, Ballwin, and August F. Ottinger, St. Louis, Mo., assignors to Monsanto Company, St. Louis,

0. N0 Drawing. Filed Apr. 3, 1968, Ser. No. 718,378 Int. Cl. D21h 1/40 US Cl. 117--76 Claims ABSTRACT OF THE DISCLOSURE This invention relates to fibrous substrates and the sequential coating thereof with an interpolymer of ethylene, vinyl chloride and acrylamide and polyvinylidene chloride polymer.

This invention relates to fibrous substrates and the coating thereof. More particularly, this invention is concerned with novel coated fibrous substrates in sheet and roll form in which the substrate may be paper, paper board, preformed paper containers, fabrics or other fibrouslike bases. The substrate is sequentially coated with an interpolymer latice of ethylene, vinyl chloride, and acrylamide with or without small quantities of other monomers, and with a polyvinylidene chloride polymer. This invention further provides that either the interpolymer or polyvinylidene chloride polymer may be used as the precoat and with the overcoat or second coating being the polymer which is not utilized as the precoat.

Fibrous substrates, such as paper, are widely used in packaging operations. Paper, however, has a very poor resistance to penetration by water vapor, gases, oil, solvents and greases. To improve the water vapor barrier resistance, paper has been coated with a variety of substances. The most common paper coating is Wax. While Wax coated paper has good Water vapor barrier resistance in a smooth or uncreased condition, it has poor resistance after it is creased. Apparently the brittleness of the wax is so great that creasing causes it to fracture and break thereby providing many areas through which water vapor can pass with little or no resistance. Additionally, wax coated paper does not serve to form a hard and scuif resistant surface.

The coating of paper with asphalt has also been tried and although good water vapor barrier resistance is obtained, the coated paper has poor resistance after being creased. Additionally, asphalt is a black, toxic material which limits its application as a paper coating; particularly in the food packaging industry. Furthermore, asphalt coatings are subject to changes in flow properties with a variance in temperature.

Paper has also been coated with a film of polyethylene. The resulting polyethylene coated paper is found to have less resistance to water vapor penetration than wax coated paper when the coat is tested in a flat or smooth uncreased condition. The polyethylene coated paper is found to be a better barrier than the wax coated paper when creased.

Plasticized polyvinyl chloride polymers are used in paper coating applications. Since the polyvinyl chloride is normally externally plasticized a loss in permanence of the resistance to water, oil, grease and solvents is experienced as a result of the extraction and bleeding of the plasticizer.

To improve oil, solvent and grease resistance and vapor resistance, paper has been treated with polyvinylidene chloride. The characteristic brittleness of polyvinylidene chloride causesfailures of such coatings with creasing. Attempts to improve this limited flexibility by the use of plasticizers and comonomers with the polyvinylidene chloride results in decreased etficiency of water barrier properties. The poor impact resistance of the polyvinylidene chloride also results in the rupture of the film during high speed scoring and creasing. The presence of plasticizers also reduces the resistance to the passage of gases and liquids.

In view of the state of the art, it has become highly desirable to discover materials which are not only useful for coating fibrous substrates but will impart good oil, grease, solvent and water vapor barrier resistance.

It is accordingly an object of this invention to provide a material which will provide improved fibrous substrate coating compositions.

It is a further object of this invention to provide a material which will provide good oil, grease, solvent and water vapor barrier properties when used as fibrous substrate coating compositions.

Other objects and advantages of the invention will be apparent to those skilled in the art from the following detailed description and claims.

In accordance with this invention it has been found that the above and still further objects are achieved when a fibrous substrate is sequentially coated With an ethylene/ vinyl chloride/acrylamide interpolymer of the type hereinafter described and with polyvinylidene chloride.

The interpolymers which are prepared and used as one of the coating compositions according to this invention in aqueous dispersion or latex form generally contain from about 5 percent to about percent ethylene, from about 30 to about 95 percent vinyl chloride, and from about 0.1 to about 10 percent of acrylamide. Part of the acrylamide in the interpolymer may be replaced by polar monomers such as acrylonitrile methacrylamide, N- (lower alkyl)acrylamide and N-(lower alkyl)methacrylamide containing from 1 to 3 carbon atoms in said lower alkyl groups, N-methylol acrylamide, N[2-(2-methyl-4- oxopentyl)]acrylamide, acrylic acid, methacrylic acid, and alkali metal and ammonium salts of acrylic and methacrylic acids, maleic acid, fumaric acid, half and complete alkali metal and ammonium salts of male-ic and fumaric acid, aconitric acid, itaconic acid, citraconic acid, and alkali metal and ammonium salts thereof half alkyl esters of maleic, fumaric, itaconic and citraconic acids having from 1 to 6 carbon atoms in each alkyl group, acrylyl and methacrylyl esters of hydroxyalkanoic acids having from 2 to about 6 carbon atoms in the alkanoic acid moieties, acrylylamides and methacrylylamides of aminoalkanoic acids having from 2 to about 6 carbons in the aminoalkanoic acid, hydroxyethyl and hydroxypropyl esters of acrylic, methacrylic, maleic, and fumaric acids, vinyl esters of alkanoic acids having from 1 to 6 carbon atoms such as vinyl acetate, vinyl propionate, and lower alkyl (1 to 6 carbon atoms) sulfonic acid, phenylsulfonic acids, and alkylphenylsulfonic acids and acrylyl and methacrylyl esters of hydroxyalkylsulfonic acids having from 1 to 6 carbon atoms in said alkyl moieties, and hydroxyalkylsulfonamides having from 1 to 6 carbon atoms in said hydroxyalkyl moieties. The acrylamide generally should constitute at least 50 percent by weight of the third or polar monomer of said interpolymer, and preferably constitutes at least about percent of said polar monomer. Thus the interpolymers as prepared in aqueous dispersed form are at least terpolymers containing ethylene, vinyl chloride, and acrylamide, and may be a quaternary or higher polymers containing one or more of the above exemplified additional polar monomers in small quantities but generally such additional monomers will not be present in the interpolymer in quantities greater than about 2 percent by weight.

It is preferred that the interpolymer contain from about 5 percent to about 70 percent ethylene, 30 percent to about 95 percent vinyl chloride, and from about 1 percent to about percent acrylamide. A specific example of choice, as presently understood, :is a terpolymer containing from about 19 to 23 percent ethylene, about 74 to about 78 percent vinyl chloride, and from about 2 to about 4 percent acrylamide.

Although the interpolymers used in the practice of this invention are generally unmodified, the modified interpolymers are included for use in this invention. Theinterpolymers are particularly amenable to h gdrolytic modiiication by the use ofsmall quantities of a strongly alkaline material such as an alkali metal hydroxide, or a quaternary ammonium hydroxide such as the mineral acids, e.g., hydrochloric, sulfuric, phosphoric, nitric. The base or acid used preferably has an ionization constant higher than l0- at 25 C.

The hydrolyzing treatment, performed with an acid or a base need not be performed to the same extent, especially if the interpolymer contains polar monomers in addition to the acrylamide. The aqueous dispersion or polymer latex of the ethylene, vinyl chloride, and acrylamide is generally treated with aqueous base or acid in an amount which is;chemically equivalent to up to about 1100 percent of the amide equivalent in the interpolymer.

. Specific examples of polar monomers which may be used, as described above, to replace part of the acrylamide in the polymers of this invention'include acrylonitrile, N-methylacrylamide, N-ethylacrylamide, N-propylacrylamide, methacrylamide, acrylic methacrylic, maleic, fumaric, itaconie, aconitic, and citraconic acids and alkali metal and ammonium salts of such acids,.preferably the sodium, potassium or ammonium salts, alkyl esters of such acids, e.g., methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, ethyl methacrylate, :monoethyl maleate, dipropyl fumarate, acrylyl 3-hydroxypropionate, methacrylyl 4-hydroxybutanoate, N-acrylylacetamide,N-methacrylyl hexamide, Z-hydroxyethyl and 2-hydroxypropyl esters of acrylic, methacrylic, maleic, fumaric, itaconic, aconitic, and citraconic acids, vinyl formate, vinyl acetate, vinyl hexanoate, vinyl and alkyl esters of propanesulfonic acid, vinyl phenylsulfonate, acrylyl and methacrylyl esters of 2-hydroxypropylsulfonic acid, and N-acrylyl and N-methacrylyl Z-hydroxypropanamides. e

The ethylene, vinyl chloride, acrylamide interpolymers may be prepared by first mixing ethylene and vinyl chloride in an aqueous medium in the presence of any suitable anionic or nonionic emulsifier and any initiator capable of generating free radicals in the chemical mixture at the chosen reaction temperature and pressure. The acrylamide, preferably in aqueous solution either alone or mixed with the appropriate amounts of other polar monomers, is added to the polymerizing ethylene and; vinyl chloride mixture gradually throughout the'reaction. Since the acrylamide is very reactive, it cannot be all added at the start of the reaction. It is preferable to deiay the addition of the acrylamide until about 40 to 50 percent of the desired'conversion of the ethylene and vinyl chloride has been reached, since, in the tfinal application of the latex, the surface of the polymer particles constitutes the locus of adhesiom'This produces a shell-core latex in which the polar monomer is concentrated in the oute layers.

The foregoing ethylene/vinyl chloride/acrylamide interpolymers are readily prepared by various means known to' the art. The ethylene/ vinyl chloride/acrylamide interpolymers used in this invention are preferably prepared by a process which comprises mixing ethylene and vinyl chloride monomers in the presence of an alkaline buffered reduction-oxidation (redox) initiator-catalyst system, water and from about 1 percent to aboutS percent by weight based upon the monomer feed, or from about 4 percent to about 7 percent based upon the polymer 'product of an anionic or nonionic emulsifying agent having tion are carried out in a 3820 ml. pressure vessel at 30 C..

at a rotary stirrer speed of 600 r.p.m. 7'

EXAMPLE 1 This example illustrates the preparation of 21/76/3 ethylene/ vinyl chloride/acrylamide terpolymer latex, and the post-stabilization of such latex with an emulsifier.

Reaction vessel initial charge: u. K S O (KPS) 11.0 NaHCO 15.0 FC(NO3)39HQO 08 Tetrasodium ethylenediaminetetraacetate (Na EDTA) 1.5 Sodium lauryl sulfate (SLS) L 1.2 Vinyl chloride (VCli' L 450 Ethylene (E) l 150 H O to make 1700 ml.

The. above ingredientmixture was heated to .30" C. with stirring to give a reaction. pressure of 850 p.s.i.g. The polymerization was started by adding a 1 Msodium formaldehyde sulfoxylate-NaHSO -CH O 2H (SFS 1.5 M ammonium hydroxide (NH OH) solution to the mixture at a rateof 5.2 ml./hr. at the same time 18- ml./hr.

of a 25 percent SLS solution was added and the pressure was kept constant by the addition of pure vinyl chloride as required. After three hours had elapsd, a 50 percent solution of acrylamide in water solution was added at 40 ml./hr. The reaction stopped after 5.5 hours and the feed streams were turned off. A total of 1330 g. of VCl, '95 ml. of the 50 percent acrylamide, 27 ml. of the 1 M SFS/LS M NH O-H solution, and 92 ml. of the 25 percent SLS solution had been added. The resulting polymer latex was vented out the bottom of the autoclave. A total of about 3500 g. of the ethylene/vinyl chloride/acrylamide polymer latex was obtained containing 47 percent total solids, and 1.5 percent,,sodium lauryl sulfate (based on the weight oftthe polymer). It had a pH of 7.7. The composition of the terpolymer was about 21/ 76/ 3 ethylene/ vinyl chloride/acrylamide. After addition of 1.5 percent of sodium dodecyl benzene sulfonate or 3% tridecyloxy (CH CH O) H, the latex was ready for use directly as a barrier coating on fibrous substrates such as paper and paperboard.

EXAMPLE 2 This example illustrates the preparation of the base modified ethylene/vinyl chloride/acrylamide terpolymer.

Using the same reaction vessel and ingredients as are described in Example 1, except that only 10.0 g. of KPS, and only 0.5 g. of SLS was used in the initial; ingredient charge. The SFS/NH OH solution Was added at the rate of 4 ml./hr. and the SL8 solution was added at 8 mL/hr. The polymerization reaction stopped after 5.75 hours with a total of about 1340 g. of vinyl chloride, ml. of acrylamide solution, 23 ml. of SFS/NH OH solution, and 43 ml. of 245 percent SLS being added. The resulting terpolymer latex was post-stabilized by mixing therewith an additional 17 ml. of 25 percent sodium lauryl sulfate (SLS). The stabilized latex was then vented from the bottom of the reaction vessel. There was obtaineda3460 g. of material conatining. 49 percent total solids, 1 percent of the SL8 and essentially the same terpolymer as dc scribed in Example 1. The particle size of this polymer latex was somewhat larger than that of Example 1.

This stabilized ethylene/vinyl chloride/acrylamide terpolymer latex was warmed at 50 C. for 4 to 16 hours after adding 0.4-2.0 g. of sodium hydroxide (added thereto as a 10 percent NaOH in water solution) per kilogram of latex.

EXAMPLE 3 A four monomer component polymer latex was prepared as follows:

A pressure reaction vessel was initially charged with 9.0 g. KPS, 12.0 g. NaHCO 0.8 g. FC(NO3) -9H 0, 1.5 g. Na EDTA, 0.5 g. SLS, H O to make 1700 ml., 575 g. E, 470 g. VCl.

This mixture was sealed and warmed to 1550 p-.s.i.g. Polymerization was started by pumping into the vessel contents a 1 M SFS/ 115 M NH OH solution at the rate of 4 ml./hr. At the same time 10 ml./hr. of a 25 percent SLS was added. Vinyl chloride sufiicient to keep the pressure constant was added throughout the reaction. At the end of 3 hours of polymerization an aqueous solution containing 40 percent acrylamide and 10 percent sodium acrylate wa added to the reactor at the rate of 24 ml./ hr. After 6 hours, the reaction stopped and a total of 491 g. of vinyl chloride, 52 ml. of 25 percent SLS, 27 ml. of SFS/NH OH and 72 ml. of the acrylamide/solution acrylate solution had been added. Unreacted ethylene and vinyl chloride were vented from the top of the reactor to lower the pressure to about 250 p.s.i.g., and then the latex was taken out through the bottom of the reactor. There was thus obtained about 3060 g. of latex containing 43 percent solids, and 1.1 percent sodium lauryl sulfate. The polymer composition was a 21/ 76/ 2.3 07 ethylene/vinyl chloride/acrylamide/sodium acrylate polymer. It was suitable for use directly as a coating composition for paper and paperboard. The procedure is repeated substituting for the sodium acrylate an equivalent amount of sodium methacrylate of substantially the same monomer portion is obtained.

interpolymers prepared in a manner analogous to the procedure described in Example 1 are shown in Table I.

TABLE I Latex,

percent VOL, Ethylene, polymer Percent Example No. percent percent Aerylamide solids SLS SLSSodium laulyl sulfate.

Latex, percent polymer Example No.

solids of Table I EXAMPLES 1 11 6 Following the procedure of Example 3 an equivalent amount of the component tabulated below is substituted for the sodium acrylate to obtain a latex polymer described below composed of substantially the same proportions as the product of Example 3.

Component=Hydroxyethyl acryl ate Polymer: Ethylene/vinyl/chloride/acrylamide/ hydroxyethylacrylate Component:N-isopropylacrylamide Polymer=Ethylene/vinyl chloride/acrylamide/ N-isopropylacrylamide Component:N-ethylmethacrylamide Polymer: Ethylene/ vinyl chloride/acrylamide/ N-ethylmethacrylamide Component=A diammonium salt of itaconic acid Polymer=Ethylene/ vinyl chloride/acrylamide/ diammonium itaconate Component=Monobutyl acid maleate Polymer=Ethylene/ vinyl chloride/acrylamide/ monobutyl acid maleate Component:N methacrylylpropionamide Polymer=Ethylene/ vinyl chloride/ acrylamide/ N-methacrylylpropionamide The fibrous substrates to which the compositions are applied in carrying out the present invention include papers of all types, such as bond writing paper, fibrous paperboards such as cardboard, chipboard, carton stock, and the like, wrapping papers or boards, or liners for containers intended for the packaging of foods, greases, chewing gum, soap, soap powders, cosmetics, calking com pounds, etc. The coated papers may also be used as wallpapers, papers for lining drawers and shelves, especially in linen closets, kitchen cabinets and so forth, and the coated paper or paperboards may be used as bookcovers or book pages.

The coatings may be applied to building construction papers and boards, such as the facing paper on plasterboard. It may be used as a release-coating on a paper to be used as a liner in a concrete molding form or adapted to be used for covering freshly-laid concrete roads.

The fibrous substrates such as paper which may be sequentially coated according to this invention with an ethylene, vinyl chloride, acrylamide interpolymer as the precoat or overcoat to produce a product of enhanced barrier characteristics may contain from about 0.5 to .90 pounds of ethylene, vinyl chloride, acrylamide interpolymers on one side per ream (a ream is 3000 sq. ft. and equals 500 sheets, 24 inches by 36 inches). Generally, however, about 1 to 20 pounds of ethylene, vinyl chloride, acrylamide interpolymers per ream is adequate while 1 to 4 pounds is all that is needed for many purposes.

The amount of polyvinylidene chloride polymer applied as a precoat or an overcoat may be varied considerably. In general, however, the useful range is about 0.1 to 20 pounds of polyvinylidene chloride polymer per ream on one side of a substrate such as paper. For most purposes, 05 to 4 pounds of polyvinylidene chloride polymer per ream is adequate.

The processes for applying the precoat and overcoat to the substrate are well known to the art. Such techniques include spraying, roller coating, air-knife coating, trailing blade coating, curtain coater and use of a Mayer rod (machine).

The following examples illustrate the advantages and unexpected properties which are achieved by the use of the ethylene, vinyl chloride, acrylamide interpolymers and polyvinylidene chloride polymers in sequentially coating fibrous substrates, but it is not intended that this invention be limited by or to the examples.

The ethylene/vinyl chloride/acrylamide interpolymers or polyvinylidene chloride polymer precoat is applied to the felt side of the paper substrate by means of a wire wound rod. Coating rod numbers 6, 18 and 28 may be utidiameter and more winds for a given rod length which deposits a light continuous wet film whereas the No. 28 rod has a larger wire diameter and fewer winds per inch which deposits a much heavier film.

The paper is mounted on a flat glass surface, the wire wound rod is placed in the draw-down bar which is positioned at the top of the sheet, latex is then poured across the paper web just in front of the draw-down bar, the draw-down bar is pulled at a uniform speed across the paper web leaving behind a uniformly even wet latex film. All precoated samples are permitted to air dry overnight, then exposed to 120 C. for 2 minutes, then calendered.

The top coat of ethylene vinyl chloride acrylamide interpolymer or polyvinylidene chloride polymer is applied to the precoated paper utilizing the same procedure as in applying the precoat.

In sequentially coating the paper with two polymer species, a drying step is provided between the two coating steps.

The coatings may also be prepared by coagulating the polymers from a latex, washing and then extruding the coating by methods known to the art.

A series of paper sheets of 50 lb. bleached kraft base stock were precoated with varying weights ethylene, vinyl chloride, acrylamide interpolymers and top coated with varying Weights of polyvinylidene chloride polymer. The moisture vapor transmission rates for creased and uncreased paper samples are shown in Table II. The oil resistance properties of the same coated papers are given in Table III.

The coatings are then tested for various physical properties. The test procedures are hereinafter described and the results are listed in Tables II and III.

The test methods used to determine the physical properties of the paper coated with ethylene, 'vinyl chloride, acrylamide interpolymer and polyvinylidene chloride polymer are listed below with explanatory notes where necessary. Samples were conditioned according to TAPPI T402m49 before testing. The paper base stock used in the testing hereinafter described is indicated for each example.

Oil resistance creased box test.-A 6" x 6" coated one side specimen blank is folded in half in each direction as well as diagonally from corner to corner, each fold i subjected to a 1b. pressure. The blank is further folded one inch from each edge and then made up into a 4" x 4" box having 1" side walls with the coated surface inside. All creases, except those made by the side walls folds converge as an apex in the center of the box bottom. 50 cc. No. 10 SAE oil is poured into the box and the time required to penetrate the creased areas is noted.

Moisture-vapor transmission rateA.-S.T.M. 3-988 (tropical atmosphere).-Reported as grams H O/100 sq. inches/24 hrs. at 100 F. and 90% relative humidity.

TABLE III.-OIL RESISTANCE P RO IERTIE S OF C O A'IED PAP E R Number penetrations Time, Along Unereased Cast film Composition see. crease area characteristic 77 15 45 Flexible. 190 4 11 D0. 328 0 3 D0. 70 5 21 D0. 238 1 9 Do. 89 11 45 Do. 121 9 50 D0. 150 2 24 Do. 67 12 50 Do. 189 3 20 Do.

The results set forth in Tables II and III show that compositions B through L impart to the paper the desirable combination of oil and water vapor resistance and good flexibility. Such combinations of properties is not attainable when polyvinylidene chloride polymer is used as the sole coating material.

Replacement of the latices 1 and 2 of compositions B through L with the latices of Examples 3 through 16 as the precoat material results in coated papers having properties similar to those presented in Tables 11 and III. The application of the interpolymer as a precoat or an overcoat imparts not only flexibility to the overall paper coating with a reduction of coating weight of polyvinylidene chloride polymer of at least 50% but moisture barrier properties are maintained which are generally equivalent to a two-pass polyvinylidene chloride polymer coating.

The paper to be coated can be of a wide variety of types including kraft, bond, parchment, etc. The type, weight and other physical properties of the paper to which the coating is applied do not significantly offer the improvement in oil resistance and moisture vapor transmission rate brought about by the method of the invention.

The coated papers provided by the present invention have utility for many purposes which will be obvious to those skilled in the art. In particular, the coated papers may be used to wrap food products where it is desired to prevent the transmission of moisture from the atmosphere to the packaged product. The coated papers are easily heat sealed and hold liquids well. As a result, such coated papers can be used in the manufacture of paper drinking cups and the like.

While this invention has been described with respect to certain embodiments, it is not so limited and it is to be understood that variations and modifications thereof may be made without departing from the spirit or scope of this invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A fibrous substrate having on at least one surface TABLE II Total Moisture vapor transmission 1 Rod Coating wt., Rod Coating wt., coating wt., Composition Latex No lbs/1,000 it. Latex No. lbs/1,000 it. lbs/1,000 it. (Increased Greased 6 4. 35 4. 35 1. 36 1. 6 2. 25 6 2. 00 4. 25 1. 77 1. 98 4 1. 40 PVDC 6 2. 80 4. 20 6. 21 7. 68 6 1. 70 6 2. 40 4. 10 3. 78 4. 8 2.10 PVDG 6 1. 68 3. 78 1. 72 1. 79 6 1. PVDC 4 2.10 3. 80 4. 75 5. 21 o 6 1.70 PVDC 8 3.45 5.15 1.21 1.97 II Example 2. 4 2. 30 PVD C 6 2. 51 4. 81 5. 98 10. 15 I .do. 6 2. 40 PVDO 6 2. 47 4 87 3. 92 5. 75 .I do. 8 2. 60 PVD C 6 1. 22 3 82 1. 98 3. 21 K o 6 2. 40 PVDO 4 2. 66 5 06 4. 25 5. 69 L- 6 2. 40 PVDO 8 3. 05 5 45 l. 41 2. 18 M PVDC 6 2.00 6 2.00 3 99 0.87

Rate g. H120/1OO sq. in./24 hrs. at 100 F. plus RH.

2 Example thereof a sequential coating comprising from about 0.5 to about 90 pounds of an interpolymer and from about 0.1 to about 20 pounds of polyvinylidene chloride polymer per each 300 square feet of fibrous substrate, provided that when the coating in immediate contact with the substrate is an interpolymer the superimposed coating is polyvinylidene chloride polymer and further provided that when the initial coating is polyvinylidene chloride polymer the superimposed coating is an interpolymer, said interpolymer being selected from the group consisting of (a) an interpolymer containing from about to about 70 percent ethylene, from about 30 to about 95 percent vinyl chloride, and from about 0.1 to about percent of at least one other polar monomer including at least about 0.1 percent to about 10 percent of acrylamide, any remainder of said polar monomer content being selected from the group consisting of acrylonitrile; methacrylamide; N-(alkyl) acrylamide and N-(alkyl) methacryl amide having from 1 to 3 carbon atoms in each alkyl group; N-methylol acrylamide; N-[2-(2-methyl-4-oxopentyl)] acrylamide; acrylic and methacrylic acid and the alkali metal and ammonium salts thereof; maleic and fumaric acids; half and complete alkali metal and ammonium salts of maleic and fumaric acids; itaconic, citraconic and aconitic acids and the alkali metal and ammonium salts thereof; half alkyl esters of maleic, fumaric, itaconic and citraconic acids having from 1 to 6 carbon atoms in each alkyl group; acrylyl and methacrylyl esters of hydroxy alkanoic acids having from 2 to 6 carbon atoms in said alkanoic acid moieties, acrylamide and methacrylamides of aminoalkanoic acids having from 2 to 6 carbon atoms in each aminoalkanoic acid moiety; hydroxyethyl and hydroxypropyl esters of acrylic, methacrylic, maleic and fumaric acids; vinyl esters of alkanoic acids having from 1 to 6 carbon atoms; alkyl sulfonic acids having from l-to 6 carbon atoms; phenyl sulfonic acids; alkyl phenyl sulfonic acids having from 1 to 6 carbon atoms in each alkyl; acrylyl and methacrylyl esters of hydroxy alkyl sulfonic acids having from 1 to 6 carbon atoms in each alkyl, and hydroxy alkyl sulfonamides having from 1 to 6 carbon atoms in each hydroxy alkyl, and (b) interpolymers of the type described in (a) treated with an acid or a base having an ionization constant higher than about 10- in amounts equivalent to up to about 100 percent of the amide content of said interpolymer.

2. A fibrous substrate in accordance with claim 1 wherein the substrate is coated with about 1 to about pounds of interpolymer and from about 0.1 to about 20 pounds of polyvinylidene chloride polymer on the interpolymer coating per each 3000 square feet of substrate.

3. A fibrous substrate in accordance with claim 1 10 wherein the substrate is coated with about 1 to about 20 pounds of interpolymer and from about 0.5 to about 4 pounds of polyvinylidene chloride polymer on the interpolymer coating per each 3000 square feet of substrate.

4. A coated fibrous substrate described in claim 1 wherein the interpolymer is a terpolymer containing from about 15 to percent ethylene, from about 30 to percent vinyl chloride and from about 0.1 to 10 percent acrylamide.

5. A coated fibrous substrate as described in claim 4 wherein the ethylene/ vinyl chloride/acrylamide terpolymer is treated with alkaline material chemically equivalent to up to about percent of the amide content of the interpolymer.

6. A coated fibrous substrate as described in claim 1 wherein the polar monomer content of said interpolymer is a combination of acrylamide and, under 2 percent of the total interpolymer Weight, of an alkali metal acrylate or methacrylate.

7. A coated fibrous substrate as described in claim 6 wherein the interpolymer is a quaternary polymer containing from about 15 to 70 percent ethylene, from about 30 to about 85 percent vinyl chloride, from about 1 percent to about 5 percent of acrylamide, and from about 0.1 to 2 percent of sodium acrylate or methacrylate.

8. A coated fibrous substrate in accordance with claim 1 wherein the substrate is paper.

9. A coated fibrous substrate in accordance with claim 1 wherein the substrate is paperboard.

10. Fibrous substrate in accordance with claim 1 wherein the polar monomer content of said interpolymer is a combination of acrylamide and N-methylol acrylamide.

References Cited UNITED STATES PATENTS 3,084,131 4/1963 McEWan et a1. 117155X 3,310,514 3/1967 TrofimoW et a1. 117155X 3,352,710 11/1967 Wolf et a1 ll716lX 3,428,582 7/1969 DeeX 117161X 3,459,591 8/1969 Konishi et a1. 117-161UX FOREIGN PATENTS 649,539 10/1962 Canada 1l776 WILLIAM D. MARTIN, Primary Examiner M. R. LUSIGNAN, Assistant Examiner US. Cl. X.R. 

